The differences of atmospheric delays (Atmospheric ties) are theoretically affected by the height differences between antennas at the same site and the meteorological conditions. However, there is often a discrepancy between the expected zenith delay differences and those estimated from geodetic analysis. The purpose of this experiment is to investigate the possibility effects that could caused biases on GNSS atmospheric delays at co-location site.

We set up the experiment on the rooftop of the A20 building at Telegrafenberg, the campus of GFZ, Potsdam, Germany. This experiment used four Septentrio choke-ring antennas (SEPCHOKE B3E6) and Septentrio PolaRx5 receivers. We installed the antenna A201 at the highest place. A202 and A203 were placed lower than A201 with two meters and four meters height differences, respectively. Antenna A204 was installed on the same level as A203 but installed with radome (SPKE). Moreover, the meteorological sensor (Vaisala WXT530) was installed to record air pressure, temperature, and relative humidity. The GNSS data were processed by using EPOS.P8 software with Precise Point Positioning (PPP) approach. The GFZ Final orbits and clock products were used in the processing. The zenith total delays and total gradients were hourly estimated. The station coordinates were estimated daily. Results of an experiment are reported in Kitpracha et al. (2021).